Musical pen with round top button



FIG. 1 is a perspective illustration embodying my new design;

FIG. 2 is a top plan view;

FIG. 3 is a front elevational view;

FIG. 4 is a left side elevational view;

FIG. 5 is a rear elevational view; and,

FIG. 6 is a bottom plan view. 

The ornamental design for a musical pen with round top button, as shown. 